JP3322380B2 - Exhaust gas measurement device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas measuring device, and in particular, extracts a part of an engine exhaust gas from an exhaust pipe and guides it to a mini-dilution tunnel. The present invention relates to an exhaust gas measurement device which is diluted with air to measure nitrogen oxides and the like.

[0002]

2. Description of the Related Art Mini-dilution tunnels are used for measuring the exhaust gas of engines, especially diesel engines. An exhaust gas measurement device using a mini-dilution tunnel extracts a part of the exhaust gas with a sampling pipe, dilutes the extracted part of the exhaust gas with air in a mini-dilution tunnel, and exhausts it into the atmosphere. The same state as in the case where gas is released appears to measure nitrogen oxides and the like.

In such an exhaust gas measuring apparatus of the mini-dilution tunnel type, the dilution tunnel becomes compact because it is not necessary to dilute the entire amount of the exhaust gas. It is possible to make the size compact.

[0004]

In such a mini-dilution tunnel type exhaust gas measuring apparatus,
The split ratio of the sampled exhaust gas is determined by the ratio of the amount of exhaust gas guided to the mini-dilution tunnel to the total amount of exhaust gas. In order to stabilize such a split ratio, conventionally, a manually operated valve is provided at the inlet of the mini-dilution tunnel and at the dilution air inlet, and such a valve is adjusted by an operator. I was

However, under conditions where the flow rate of exhaust gas is small, such as when the engine is idling, etc.
A stable split ratio could not be obtained by the above method. If the split ratio was not stable due to engine operating conditions or disturbances, the operator further opened and closed the dilution air adjustment valve, but the adjustment was delicate, and this adjustment was more difficult during operation. There were problems such as difficulty.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has been made in consideration of the above problems, and has an exhaust gas in which a split ratio is further stabilized by automatically adjusting an amount of air guided to a mini-dilution tunnel. It is an object to provide a measuring device.

According to the present invention, a part of the exhaust gas of an engine is extracted from an exhaust pipe and led to a mini-dilution tunnel, and the exhaust gas is diluted with air in the mini-dilution tunnel to measure nitrogen oxides and the like. And a NOx meter for detecting the concentration of nitrogen oxides in the exhaust gas and the concentration of nitrogen oxides in the mini-dilution tunnel, respectively. Calculating means for calculating a division ratio of exhaust gas by an amount of nitrogen oxides in the exhaust gas with respect to an amount of nitrogen oxides in the mini-dilution tunnel obtained based on a concentration of nitrogen oxides; Automatic adjustment means for automatically adjusting the amount of air introduced into the tunnel so that the exhaust gas division ratio based on the calculation is constant. It relates exhaust gas measuring apparatus according to claim and.

[0008]

The amount of dilution air introduced into the mini-dilution tunnel is adjusted by the automatic adjusting means, and the division ratio of the exhaust gas is stabilized.

[0009]

FIG. 1 shows an entire configuration of an exhaust gas measuring apparatus according to an embodiment of the present invention. An exhaust pipe 11 is provided on an exhaust manifold 11 mounted on a side of a diesel engine 10. It is connected. The exhaust pipe 12 has a butterfly valve 13 for adjusting exhaust pressure and a muffler 1.
4 is connected.

The outlet side of the muffler 14 is connected to another exhaust pipe 15. A pulsation preventing resonator 16 is connected to the exhaust pipe 15 so as to branch off. The upper end side of the exhaust pipe 15 is open to the atmosphere, and a part of the exhaust pipe 15 which is open to the air faces the inlet of the flue 17. An exhaust blower 1 is provided at the tip of the flue 17.
8 are connected.

An intake manifold is attached to a portion opposite to the engine 10, and an intake pipe 19 is connected to a tip end of the intake manifold. A flowmeter 20 is further connected to the intake pipe 19.

The exhaust gas measuring device includes a mini-dilution tunnel 22. The entrance of the mini-dilution tunnel 22 is connected to an air introduction pipe 23. An air pump 24 for introducing dilution air is provided at the distal end of the air introduction pipe 23. The distal end side of the air introduction pipe 23 provided with such an air pump 24 is opposed to the end of the dilution air supply pipe 25 in an open state.

On the other hand, a heat exchanger 27 is connected downstream of the mini-dilution tunnel 22, and a blower 28 is connected downstream of the heat exchanger 27. The blower 28 is a blower that rotates at a constant rotation speed.

A bypass orifice 29 is attached to an upright portion of the exhaust pipe 15 connected to the downstream side of the muffler 14, and a sampling pipe 30 is inserted below the orifice 29. The exhaust gas is extracted by the pipe 30 and introduced into the mini-dilution tunnel 22. A sampling orifice 31 is attached to the sampling tube 30.

The orifice 29 of the exhaust pipe 15 and the orifice 31 of the sampling pipe 30 each serve as a throttle, and the flow rate of the exhaust gas flowing to each of the two orifices 29 and 31 is distributed according to the ratio of the air resistance. Is done. Since the input pressure of each orifice 29, 31 is the same and constant at the sample point, controlling the output pressure will change the distribution ratio of the exhaust gas.

A small-diameter thin tube having a sampling pump 32 for sampling a part of the exhaust gas diluted in the mini-dilution tunnel 22 is inserted into the mini-dilution tunnel 22. A NOx meter 33 is connected downstream of the sampling pump 32.

Further, a mini dilution tunnel 22
Another capillary inserted in the filter is a particulate filter 34, a sampling pump 35, and a flow meter 36.
And are connected respectively.

A pretreatment device 37 is connected to a thin tube inserted below the exhaust pipe 15 which is on the outlet side of the muffler 14 and stands upright. A NOx meter 38 is connected downstream of the pretreatment device 37.

In the above configuration, the exhaust gas generated by the operation of the engine 10 shown in FIG. 1 is taken out through the exhaust manifold 11 and the exhaust pipe 12. At this time, the exhaust pressure is adjusted by the exhaust pressure adjusting butterfly valve 13 and the exhaust pulsation is reduced by the muffler 14. Then, a part of the exhaust gas passing through the exhaust pipe 15 is extracted by the sampling pipe 30 and guided to the mini-dilution tunnel 22.

In the mini-dilution tunnel 22, the exhaust gas is diluted by the atmosphere introduced through the air introduction pipe 23. The atmosphere for such dilution is supplied by a dilution air supply pipe 25, and the air supplied from the supply pipe 25 is sucked by an air introduction pipe 23 by an air pump 24.

The diluted exhaust gas is sampled by a sampling pump 32 and led to a NOx meter 33, where the amount of nitrogen oxides is measured. Further, the diluted exhaust gas is sucked by the sampling pump 35 and passes through the particulate filter 34,
At this time, the amount of the particulates captured by the filter 34 is measured.

The state of the exhaust gas of the engine 10 before being diluted is directly extracted from the exhaust pipe 15 at the outlet side of the muffler 14, and after the exhaust gas is pre-processed by the pre-processing device 37, the NOx is measured. 38.

Next, a configuration for adjusting the amount of air sucked into the mini-dilution tunnel 22 through the air introduction pipe 23 will be described. As shown in FIG. 2, an air pump connected to the air introduction pipe 23 24 is the motor 4
2 is driven to rotate. The rotation speed of the motor 42 is controlled by an inverter 43. Moreover, the inverter 43 is adjusted based on a signal from the computer 44.

The computer 44 receives the flow rate in the mini-dilution tunnel 22, the flow rate of the exhaust gas, the NOx concentration in the mini-dilution tunnel 22, and the NOx concentration of the exhaust gas before dilution. ing. The flow rate in the mini-dilution tunnel 22 is measured by a method based on the flow rate measurement method in the dilution tunnel. The exhaust gas flow rate is measured as the sum of the absorbed air amount and the fuel flow rate. The NOx concentration in the mini-dilution tunnel 22 is measured by a NOx meter 33. The NOx concentration in the exhaust gas before dilution is measured by the NOx meter 38.

The split ratio of the exhaust gas in the mini-dilution tunnel 22 of the exhaust gas measuring apparatus shown in FIG. 1 depends on the amount of nitrogen oxide in the exhaust gas of the engine 10 and the amount of nitrogen oxide in the mini-dilution tunnel 22. And is expressed by the following equation:

(Equation 1) Each quantity in the above formula is a computer 4 shown in FIG.
4, the division ratio is automatically calculated based on the information. Then, the calculated division ratio is compared with a reference division ratio, and if the calculated division ratio is deviated from the reference division ratio, the computer 44 adjusts the rotation speed of the motor 42 via the inverter 43. Therefore, the motor 42 drives the pump 24 at an appropriate rotation speed, and the amount of dilution air introduced into the mini-dilution tunnel 22 is automatically adjusted to an optimum value.

Therefore, the mini dilution tunnel 22
In the measurement of the amounts of nitrogen oxides and particulates in the exhaust gas diluted by the above, the split ratio of the exhaust gas introduced into the mini-dilution tunnel 22 is automatically stabilized.

FIG. 3 shows a modification. In this modification, a manual adjustment valve 47 is connected together with the pump 24 to the air introduction pipe 23 on the inlet side of the mini-dilution tunnel 22. And the manual adjustment valve 47
And a fine adjustment valve 49 is provided in the bypass line 48, and the fine adjustment valve 49 is controlled by a motor 50. The number of rotations of the motor 50 is controlled by a servo circuit 51. The servo circuit 51 is controlled by the computer 44.

The manual adjustment valve 47 is manually fixed at an appropriate value, whereas the fine adjustment valve 49 has a constant exhaust gas division ratio in the mini-dilution tunnel 22. As described above, the computer 44 performs the calculation, and when there is a deviation from the reference division ratio, the motor 5
0 is adjusted to adjust the degree of opening of the fine adjustment valve 49.

Therefore, even in such a configuration, the amount of air guided to the mini-dilution tunnel 22 through the air introduction pipe 23 is controlled so that the exhaust gas split ratio is constant, and the mini-die is controlled. The division ratio of the exhaust gas introduced into the solution tunnel 22 is automatically stabilized.

[0030]

As described above, according to the present invention, the concentration of nitrogen oxides in the exhaust gas and the concentration of nitrogen oxides in the mini-dilution tunnel are detected by the NOx meter, respectively. Calculating a division ratio of the exhaust gas according to the amount of nitrogen oxides in the exhaust gas with respect to the amount of nitrogen oxides in the mini-dilution tunnel by calculation means based on the concentration of nitrogen oxides to be obtained; The amount of air introduced into the tunnel is adjusted by automatic adjusting means so that the division ratio of the exhaust gas becomes constant.

Therefore, the exhaust gas discharged from the engine is extracted at a certain stable split ratio and diluted in the mini-dilution tunnel, so that more accurate measurement of nitrogen oxides and the like can be performed. Become.

[Brief description of the drawings]

FIG. 1 is a piping diagram illustrating an overall configuration of an exhaust gas measurement device.

FIG. 2 is a block diagram showing a configuration for controlling the amount of dilution air to be constant.

FIG. 3 is a block diagram showing a configuration for automatically adjusting the amount of dilution air according to a modification.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Engine 11 Exhaust manifold 12 Exhaust pipe 13 Butterfly valve for exhaust pressure adjustment 14 Muffler 15 Exhaust pipe 16 Resonator 17 Flue 18 Exhaust blower 19 Intake pipe 20 Flow meter 22 Mini dilution tunnel 23 Air introduction pipe 24 Air pump 25 Diluted air Supply pipe 27 Heat exchanger 28 Blower 29 Bypass orifice 30 Sampling pipe 31 Sampling orifice 32 Sampling pump 33 NOx meter 34 Particulate filter 35 Sampling pump 36 Flow meter 37 Preprocessing device 38 NOx meter 42 Motor 43 Inverter 44 Computer 47 Manual adjustment valve 48 bypass line 49 fine adjustment valve 50 motor 51 servo circuit

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Claims (1)

(57) [Claims] 1. A part of the exhaust gas of an engine is extracted from an exhaust pipe and led to a mini-dilution tunnel. The exhaust gas is diluted with air in the mini-dilution tunnel to measure nitrogen oxides and the like. An NOx meter for detecting a concentration of nitrogen oxides in exhaust gas and a concentration of nitrogen oxides in the mini-dilution tunnel, respectively; Calculating means for calculating a division ratio of exhaust gas according to an amount of nitrogen oxides in the exhaust gas with respect to an amount of nitrogen oxides in the mini-dilution tunnel obtained based on the concentration of the substance; Automatic adjusting means for automatically adjusting the amount of air introduced into the exhaust gas based on the calculation so that the division ratio of the exhaust gas is constant. To exhaust gas measuring device.